The present invention relates to a method of photochemically modifying the surface of a solid workpiece to be surface-treated, e.g., formed of a synthetic resin, glass, a metal, an animal or a plant, or a ceramic, by bringing a liquid compound in or a compound solution into contact with the surface of the solid workpiece, preferably by using a capillary phenomenon, and irradiating the sample with light in this state. The present invention also relates to an adhesion method and a marking method using this surface modification method, and an apparatus for carrying out these methods.
There are known a method in which for the purpose of modifying the surface of a fluoroplastic, which is difficult to adhere because of its small affinity for other substances, a fluoroplastic is immersed in a treatment solution comprising liquid ammonia or naphthalene containing metal sodium and tetrahydrofuran to modify the surface, as well as a method of chemically modifying the surface of a polyethylene or polypropylene resin, which is chemically inactive and therefore difficult to directly print or adhere, by dipping into a mixed solution of potassium dichromate with concentrated sulfuric acid.
Unfortunately, these conventional chemical modification methods have problems in that, in the case of a fluoroplastic, for example, the surface of a fluoroplastic material turns brown to make the surface layer brittle, resulting in peeling of the adhesive layer. Consequently, no satisfactory adhesive strength can be obtained. In addition, although the above conventional methods can modify an entire portion which is immersed, they cannot perform partial modification unless a photoresist is used as a mask. Also, the treatment reaction is difficult to control, and dangerous chemicals must be used.
There are some other known methods, such as sputtering, corona discharge, and plasma processing, by which the surface of a fluoroplastic or the like is physically modified. However, because of the lack of chemical affinity for an adhesive, a roughened surface formed acts as a stress concentration point, bringing about bonding breakdown. This makes it impossible to obtain a high bonding strength.
A polymeric porous membrane or film made from a fluoroplastic, such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride, or from a polyethylene or polypropylene resin is being used as a filtering membrane in precision filtration and ultrafiltration of liquids such as chemicals, foods, and water. Several methods are known as a means for imparting hydrophilicity to these porous membranes in order to improve the rate of permeation of liquids. Examples are a method of coating a surface active agent, and a method as described in Jpn. Pat. Appln. KOKAI Publication No. 56-63772, in which pores of a porous body are impregnated with a water-soluble polymer, such as polyvinyl alcohol or polyethylene glycol, and hydrophilicity is imparted to the porous body by, e.g., a heat treatment, acetal conversion, esterification, a dichromic acid treatment, or irradiation of ionizing radiation. There is another known method by which the surface of a fluoroplastic is modified by giving hydrophilicity to the surface by irradiation of an ArF laser, as disclosed in Jpn. Pat. Appln. KOKOKU Publication No. 5-77692.
In the method of coating a surfactant, however, the surfactant is readily removed since it does not strongly adhere to a porous body, resulting in difficult in keeping hydrophilicity.
In the method described in Jpn. Pat. Appln. KOKAI Publication No. 56-63772, deterioration by decomposition of a porous body is brought about if, for example, irradiation is used, and this significantly decreases the mechanical strength. In addition, the use of a heat treatment, acetal conversion, or esterification poses a problem of a low degree of hydrophilicity, since a portion of the water-soluble polymer is given hydrophobicity.
Also, the method described in Jpn. Pat. Appln. KOKOKU Publication No. 5-77692 is a method of modification of a surface layer; i.e., it is not possible to sufficiently impart hydrophilicity to the bulk of a porous body.
The present invention has been made in consideration of the above situations and has as its object to provide a method in which a liquid which is safe at room temperature is brought into contact with the surface of a workpiece (a material to be modified), and in this state light such as ultraviolet light is irradiated on the surface of the workpiece to selectively and effectively substitute the surface with an arbitrary functional group with no damage to the surface at all, thereby modifying the surface of the workpiece. The present invention also provides a treatment apparatus for this method.
Preferably, it is an object of the present invention to provide a method in which the liquid described above is forced to closely contact, as an extremely thin layer, with the surface of a workpiece by using a capillary phenomenon or the like, and in this state light such as ultraviolet light is irradiated on the surface of the workpiece to selectively and effectively substitute the surface with an arbitrary functional group with no damage to the surface at all, thereby modifying the surface of the workpiece, and to provide a treatment apparatus for this method.
The use of a liquid as a surface modifier allows a high-density, uniform treatment, since the density of contact with an object to be treated is high compared to a gas. The use of a liquid is also advantageous from the standpoint of environment because only an exposed portion is activated by light such as ultraviolet radiation.
Incidentally, when laser light is incident on a solution of the type discussed above, bubbles are usually generated by photo-decomposition, and consequently a treatment solution on the interface of an object to be treated is removed from the interface. Then, an effective chemical reaction may not take place. Additionally, if the contact angle, with a reaction solution of the surface of an object to be treated is large, the area of contact with the liquid surface becomes small. This contact area is further decreased by generation of bubbles described above.
In the present invention, therefore, the space between the surface of glass as an entrance window for light such as ultraviolet radiation and the surface of a workpiece is made very thin. Consequently, a reaction solution enters this portion to permit formation of a thin liquid film on the surface of a workpiece regardless of the contact angle of the material with the solution. When light such as ultraviolet radiation is irradiated on the surface of the workpiece in this state, not only the liquid but the surface of the workpiece can be sufficiently excited because of a short path in the liquid. This makes effective optical modification feasible.
As discussed above, the surface layer of a solid workpiece can be photochemically, modified effectively by interposing a thin film of a reaction solution between the surface of the solid workpiece and transparent glass by using capillarity, and irradiating light on the surface of the workpiece in this state.
That is, the present invention provides a solid surface modification method, wherein a liquid compound or a compound solution is kept in contact with the surface of a solid material to be treated, radiation selected from the group consisting of ultraviolet radiation, visible radiation, and infrared radiation is irradiated on the interface between the surface of the solid material and the liquid compound or compounds in solution to optically excite the surface of the solid material and the liquid compound or compound solution, thereby effecting substitution with a chemical species in the liquid compound or compound in solution, depositing the chemical species, or performing etching with the chemical species.
According to one preferable aspect of the present invention, a thin layer of the liquid compound or compound in solution is brought into contact with the surface of a solid material to be treated, and in this state ultraviolet radiation, visible radiation, or infrared radiation is irradiated on the interface between the surface of the solid material and the liquid compound or compound in solution. As a preferable means of forming this thin layer of the liquid compound or of the compound in solution, a transparent window is kept in close proximity with the upper surface of a solid material to be treated, and the thin layer is made to be interposed between them by using capillarity. In this state, radiation selected from ultraviolet radiation, visible radiation, and infrared radiation is irradiated through the transparent window to excite the surface of the solid material, thereby effecting substitution with a chemical species in the liquid compound or compound in solution, performing etching with the chemical species, or depositing the chemical species.
As the transparent window, it is possible to use any of ultraviolet-transmitting glass, rock crystal, synthetic quartz glass, pyrex glass, optical glass, plate glass, sapphire, diamond, TiO2, IRTRAN, Ge, Si, barium fluoride, magnesium fluoride, calcium carbonate, lithium fluoride, calcium fluoride, a fluoroplastic, an acrylic resin, a styrene resin, and a carbonate resin.
The shape of the transparent window can be any of a plate, a cylinder, a sphere, a donut, and a mold. The solid material to be treated can be any of a plastic, a metal, an animal a plant, and a ceramic.
As the liquid compound, it is possible to use any of water, pure water, heavy water, an alcohol, petroleums, an aromatic compound, silicone oil, FOMBLIN oil, trichloroethylene, fluorocarbons (fluorocarbon (freon) 113 and fluorocarbon (freon) 113a), hydrogen peroxide, HCl, H2SO4, HNO3, HCOOH, (COOH)2, CH3COOH, NH3, N2H4, and NH4F.
A solvent can be selected from water, pure water, heavy water, ammonia, sulfuric acid, carbon tetrachloride, carbon disulfide, hydrocarbons, halogen compounds, alcohols, phenols, an organic acid and a derivative thereof, nitrites, nitro compounds, amines, sulfur compounds, petroleums, and ethers.
Radiation usable in the present invention can be selected from an excimer laser, an Ar+ laser, Kr+ laser, an N2 laser, a harmonics ultraviolet laser obtained by a nonlinear material, a D2 lamp, a high-pressure mercury lamp, a low-pressure mercury lamp, an Xe lamp, an Hgxe2x80x94Xe lamp, a halogen lamp, an excimer lamp, and an ultraviolet lamp obtained by an arc, corona, or silent discharge in an atmosphere of air, nitrogen, or some other gas.
If the solid material to be treated is a fluoroplastic material, a solution having an atom, such as B, Al, Ba, Ga, Li, H, or Ti, whose bonding energy to a fluorine atom is larger than 128 kcal/mol, which is the bonding energy between a carbon atom and a fluorine atom, and a functional group with affinity for an adhesive, such as one selected from xe2x80x94OH, xe2x80x94Cl, xe2x80x94NO2, xe2x80x94CN, xe2x80x94NH2, xe2x80x94COOH, xe2x80x94CO, xe2x80x94OCH3, xe2x80x94OC2H5, xe2x80x94OC3H7, xe2x80x94OC4H9, xe2x80x94CONH, xe2x80x94CH3, xe2x80x94C2H5, xe2x80x94CH2, xe2x80x94SO3H, xe2x80x94C3H7, xe2x80x94C4H9, and xe2x80x94C6H5, is brought into contact with the surface of the fluoroplastic material, and in this state ultraviolet radiation in an amount sufficient to liberate fluorine from the fluoroplastic material, i.e., at at least a photoenergy corresponding to the bonding energy of 128 kcal/mol is irradiated on the interface between the fluoroplastic material and the solution. Consequently, it is possible to liberate fluorine from the fluoroplastic material and at the same time substitute the fluorine with this functional group, thereby performing surface modification. This surface-modified fluoroplastic material can be easily bonded to a material of the same kind or a different kind via the adhesive.
That is, the present invention provides a method of bonding a fluoroplastic material, wherein prior to bonding a fluoroplastic material to a material of the same type or a different type via adhesion, the fluoroplastic material is brought into contact with a solution containing a compound having an atom with a bonding energy to a fluorine atom of 128 kcal/mol or more and one of a hydrophilic group, a lipophilic group, and a functional group inherent in an adhesive, and in this state ultraviolet radiation with a photon energy of 128 kcal or more is irradiated on the interface between the fluoroplastic material and the solution, thereby performing surface modification in which the fluoroplastic material is defluorinated and substitution is done by the functional group having affinity for the adhesive.
In addition, the present invention provides a method of manufacturing a fluoroplastic composite material, wherein fluoroplastic materials subjected to surface modification by the method described above, or such a surface-modified fluoroplastic material and a resin material of a different kind, are bonded by pressure with an organic solvent in which the materials are soluble.
Furthermore, the present invention provides a method of marking a fluoroplastic material, wherein an ink or paint containing a compound having an atom with a bonding energy to a fluorine atom of 128 kcal/mol or more and one of a hydrophilic group, a lipophilic group, and a functional group inherent in an adhesive is coated on a fluoroplastic material, and ultraviolet radiation with a photon energy of 128 kcal or more is irradiated on the interface between them.
In the present invention, fluoroplastics include a resin made from a polymer or a copolymer of monomers, which contains fluorine atoms, and a resin containing this resin as a base material. Examples are polytetrafluoroethylene, polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene, and polyvinylidenefluoride.
Examples of the compound having an atom with a bonding energy to a fluorine atom of 128 kcal/mol or more are a boron compound, an aluminum compound, a barium compound, a gallium compound, a lithium compound, a hydrogen compound, and a titanium compound. Practical examples of the compound are (BHNH)3, LiBH4, NaBH4, KBH4, CsBH4, H3BO3, B(CH3)3, B(C2H5)3, B(C3H7)3, B(C4H9)3, B(C6H5)3, B(OH)2(C6H5), NaB(C6H5)4, B(CH3O)3, B(C2H5O)3, B(C4H9O)3, (NH4)2B4O7, Al(OH)3, Al(NO3)3, AlCl3, AlBr3, AlI3, Al2(SO4)3, Al(CH3COO)2OH, Al2BaO4, NH4AlCl4, LiAlH4, ALNa(SO4)2, AlK(SO4)2, Al(NH4)SO4, Al(CH3)3, Al(C3H7)3, Al(C2H5)3, Al(C6H5)3, Al(C2H5O)3, Al(C3H7O)3, Al(C4H9O)3, Ba(ClO4)2, BaBr, BaI2, Ba(OH)2, BaS2O3, Ba(NO2)2, Ba(CN)2, GaCl3, GaBr, Ga(OH)3, Ga(SO4)3, Ga(NO3)3, Ga(CH3COO)3, GaK(SO4)2, Ga(CH3)3, Ga(C2H5)3, Ga(C3H7)3, Ga(C4H9)3, Ga(C6H5)3, LiCl, LiBr, LiI, LiOH, LiSH, LiN, LiNO3, Li(CH3), Li(hydrocarbon compound), Li(C6H5), LiCH3O, LiAlH[OC(CH3)3]3, LiNH2, H2O, D2O, H2O2, HCOOH, CH3COOH, HCl, HNO3, H2SO4, C6H6, C6H5CH3, Ti(CH2C6H5)4, [Ti(C6H5)2]2, TiCl3, TiBr4, and TiI4.
Examples of the functional group with affinity for an adhesive are xe2x80x94OH, xe2x80x94Cl, xe2x80x94NO2, xe2x80x94CN, xe2x80x94NH2, xe2x80x94COOH, xe2x80x94CO, xe2x80x94OCH3, xe2x80x94OC2H5, xe2x80x94OC3H7, xe2x80x94OC4H9, xe2x80x94CONH, xe2x80x94CH3, xe2x80x94C2H5, xe2x80x94CH2, xe2x80x94SO3H, xe2x80x94C3H7, xe2x80x94C4H9, and xe2x80x94C6H5.
If a boron compound, an aluminum compound, a barium compound, a gallium compound, or a lithium compound is a liquid at room temperature, it is only necessary to irradiate ultraviolet radiation with a photon energy of 128 kcal or more onto the interface with a workpiece in the liquid. If the compound is in a solid or powder form, the compound is dissolved in a solvent such as water, heavy water, ammonia, sulfuric acid, carbon tetrachloride, carbon disulfide, hydrocarbons, halogen compounds, alcohols, phenols, an organic acid or its derivative thereof, nitrites, nitro compounds, amines, or sulfur compounds, and ultraviolet radiation with a photon energy of 128 kcal or more is irradiated onto the interface with a workpiece in the resultant solution.
Examples of ultraviolet radiation with a photon energy of 128 kcal or more are an ArF excimer laser, an Hg lamp, and an Hgxe2x80x94Xe lamp. An ArF excimer laser can be shaped into a linear beam by a cylindrical lens and irradiated along the interface between a fluoroplastic material being continuously pulled up from the solution and the solution. It is also possible to irradiate an ArF excimer laser via a pattern corresponding to a bonding portion of a fluoroplastic material. Ultraviolet radiation can also be one from an ultraviolet lamp obtained by an arc, corona, or silent discharge in an atmosphere of air, nitrogen, or some other gas.
A solution containing a compound having an atom with a bonding energy to a fluorine atom of 128 kcal/mol or more and one of a hydrophilic group, a lipophilic group, and a functional group inherent in the adhesive can be mixed in the adhesive in advance. In addition, it is also possible to coat the resultant mixture on the surface of the fluoroplastic material, and to irradiate ultraviolet radiation with a photon energy of 128 kcal or more on the interface of the coating layer to form an adhesive layer on the surface of the fluoroplastic material. Furthermore, a porous material can be impregnated with a solution containing a compound having an atom with a bonding energy to a fluorine atom of 128 kcal/mol or more and one of a hydrophilic group, a lipophilic group, and a functional group inherent in the adhesive. In this case, the resultant porous material is kept in tight contact with the fluoroplastic material, and in this state ultraviolet radiation with a photon energy of 128 kcal or more is irradiated on the interface between them.
According to the present invention as discussed above, fluorine is liberated or extracted from the surface of a fluoroplastic material, and this fluorine is replaced by a functional group with affinity for an adhesive. As a result, the affinity of the surface of the fluoroplastic material for the adhesive is improved to achieve a high adhesive strength.
If a solid material to be treated is a plastic material having a Cxe2x80x94H bond, a liquid of a compound containing an atom, e.g., B, P, S, Pt, Br, O, Cl, H, or F, whose bonding energy to a hydrogen atom is larger than 80.6 kcal/mol, which is the bonding energy between a carbon atom and a hydrogen atom, a functional group (atomic group), such as xe2x80x94OH, xe2x80x94NO2, xe2x80x94CN, xe2x80x94NH2, xe2x80x94COOH, xe2x80x94CO, xe2x80x94OCH3, xe2x80x94OC2H5, xe2x80x94OC3H7, xe2x80x94OC4H9, xe2x80x94CONH, xe2x80x94CH3, xe2x80x94C2H5, xe2x80x94CH2, xe2x80x94SO3H, xe2x80x94C3H7, xe2x80x94C4H9, or xe2x80x94C6H5, or a metal atom, is brought into contact with the surface of the plastic material having a Cxe2x80x94H bond or with a porous body. Surface modification can be performed in this state by irradiating ultraviolet radiation with a photon energy of 80.6 kcal or more onto the interface between the surface of the plastic material and the compound having both the atom and the atomic group or metal atom described above, or a mixture of the compound.
That is, the present invention provides a method of modifying a plastic material having a Cxe2x80x94H bond with excitation light, wherein a liquid of a compound or of a mixture, which contains a first atom with a bonding energy to a hydrogen atom of 80.6 kcal/mol or more and a second atom or atomic group whose bonding energy to the first atom is smaller than an optical energy of excitation light, is brought into contact with the plastic material, and in this state ultraviolet radiation with a photon energy of 80.6 kcal or more is directly or indirectly irradiated on the interface between the plastic material and the compound or mixture, thereby liberating or extracting hydrogen from the plastic material via the first atom and at the same time substituting the hydrogen with the second atom or atomic group.
The compound containing the second atom or atomic group whose bonding energy to the first atom is smaller than the optical energy of the excitation light is a liquid containing a compound selected from a boron compound, a phosphorus compound, a sulfur compound, a platinum compound, a bromine compound, an oxygen compound, a chlorine compound, a hydrogen compound, and a fluorine compound.
Practical examples of the compound are (BHNH)3, B(CH3)3, B(C2H5)3, B(C6H5)3, B(OH)2(C6H5), P(CN)3, P2Se5, P(CH3)3, P(C2H5)3, P(C3H7)3, P(C4H9)3, P(C6H13)3, P(CH3)2(C6H5), P(CH3)(C6H5)2, P(C6H17)3, P(C6H13)3, P(C8H17)3, P(CH3C6H4)3, (SCN)2, SO2(NH2)2, Pt(CN)2, Pt(SO4)2, BrCN, Br2O, Br2CF2, BrCF3, NO, NO2, H2O2, O3, Cl2O, ClCN, AgCl, AlCl3, AsCl3, AuCl, AuCl3, BaCl2, BeCl2, BiCl3, CaCl2, CdCl2, CeCl3, CoCl2, CrCl2, CsCl, CuCl, CuC12, ErCl3, EuCl2, EuCl3, FeCln, GaCl3, GdCl3, GeCl4, H3BO3, Na2[Pt(OH)6], K2[Pr(OH6)], O2, CClF3, CCl2F2, pure water, heavy water, (COOH)2, CF4, CHF3, HgCl2, HoCl3, InCl, IrCl4, KCl, LiCl, LuCl3, MgCl2, MnCl2, MoCln, NCl3, NH4Cl, NaCl, NbCl5, NiCl2, PCl3, PbCl2, PtCln, RbCl, ReCl3, SCln, SbCl3, SeCln, SiCl4, SnCln, SrCl2, TaCl2, TbCl3, TeCln, ThCl4, TiCl3, TICl3, TmCl3, UCln, VCln, WCl6, YCl3, ZnCl2, ZrCl4, H2O, NH3, HCOOH, NH3OH, H2SO4, HCl, HNO3, HCF3, alcohols, hydrocarbons, aromatics, AgF, ASF3, BaF2, BeF2, BiF3, CdF2, CeF3, CoF2, CsF, CuF, GeF2, KF, MoFn, NH4F, NaF, NbF5, NiF, UF6, VFn, ZnF2, and CF4.
Examples of the atomic group are xe2x80x94OH, xe2x80x94NO2, xe2x80x94CN, xe2x80x94NH2, xe2x80x94COOH, xe2x80x94CO, xe2x80x94OCH3, xe2x80x94OC2H5, xe2x80x94OC3H7, xe2x80x94OC4H9, xe2x80x94CONH, xe2x80x94CH3, xe2x80x94C2H5, xe2x80x94CH2, xe2x80x94SO3H, xe2x80x94C3H7, xe2x80x94C4H9, and xe2x80x94C6H5.
The above compound can be dissolved in a solvent such as water, pure water, heavy water, ammonia, sulfuric acid, carbon tetrachloride, carbon disulfide, hydrocarbons, halogen compounds, alcohols, phenols, organic acids and derivatives thereof, nitriles, nitro compounds, amines, or sulfur compounds.
The ultraviolet radiation with a photon energy of 80.6 kcal or more is one or a combination of excimer lasers, such as XeF, XeCl, KrF, and ArF lasers, an N2 laser, a Kr ion laser, an Ar ion laser, and harmonics laser light by a nonlinear element, one or a combination of an Hg lamp, an Hexe2x80x94Xe lamp, a D2 lamp, and an excimer lamp, or one or a combination of ultraviolet radiations obtained by an arc, corona, or silent discharge in an atmosphere of air, nitrogen, or some other gas.
If the bonding energy of a side chain, except for a Cxe2x80x94H bond, which constitutes a plastic material, is smaller than a photon energy of excitation light for optically decomposing the compound, ultraviolet radiation whose photon energy is 80.6 kcal or more and smaller than the bonding energy of a side chain except for the Cxe2x80x94H bond can be directly irradiated on the plastic material, and another ultraviolet radiation with a photon energy larger than the bonding energy of the compound can be irradiated on the compound so as not to directly illuminate the plastic material (it can, for example, be irradiated parallel to the surface of the plastic material).
In this case, it is possible to use an XeF, XeCl, or KrF laser as ultraviolet radiation to be directly irradiated on the plastic material having the Cxe2x80x94H bond, and an XeCl, KrF, or ArF laser as ultraviolet radiation to be indirectly incident parallel to the surface of the plastic material.
In addition, an Hg or Hgxe2x80x94Xe lamp light with a wavelength of 300 nm or more can be used as ultraviolet radiation to be directly irradiated on the plastic material having the Cxe2x80x94H bond, and an Hg, Hgxe2x80x94Xe, D2, or excimer lamp with a wavelength of 300 nm or more can be used as ultraviolet radiation to be indirectly incident parallel to the surface of the plastic material.
As described above, hydrogen atoms on the surface of a plastic material must be liberated from the surface of the plastic material before being substituted with the atomic group or the metal atom. Since the energy of this Cxe2x80x94H bond is 80.6 kcal/mol, it is necessary to break the bond by irradiating an optical energy larger than this energy. To prevent recombination of H and C atoms, however, an atom with a bonding energy larger than that of the C atom must be present near the H atom.
Comparison of bonding energies is presented below. In this comparison, each number is expressed in kcal/mol.
The larger the bonding energy, the larger the power of dehydrogenation. Examples of a compound of an atom capable of dehydrogenation are shown in claim 2. Although dehydrogenation is possible by B, P, S, Pt, or Br whose bonding energy is relatively low, O, Cl, H, and F are practical. Of these atoms, H and F atoms have the strongest dehydrogenation power. To be precise, it is desirable that the photon energy to be irradiated be smaller than the bonding energy of a molecule bonded to hydrogen.
A liquid of a compound or of a mixture, which contains the atom and the atomic group (functional group) for dehydrogenation, or a compound dissolved in a solvent, is brought into contact with a plastic material having a Cxe2x80x94H bond, and ultraviolet radiation with energy required to break the Cxe2x80x94H bond and the bond of dehydrogenation atom of the compound is irradiated on the interface between them. Consequently, dehydrogenation and substitution reactions occur simultaneously, modifying the surface of the plastic material.
If the bonding energy for decomposing the compound is larger than the energy of the Cxe2x80x94H bond, ultraviolet radiation with a high photon energy is irradiated parallel to the surface of a plastic material, and at the same time ultraviolet radiation with a lower photon energy (higher than 80.6 kcal) is irradiated perpendicularly to the plastic material, in order to decompose only the compound in the vicinity of the plastic material. This allows more effective modification.
In the present invention as discussed above, hydrogen is liberated from the surface of a plastic material having a Cxe2x80x94H bond, and this hydrogen is substituted with various types of functional groups or metal atoms. As a result, the surface of the plastic material acquires wettability, printing properties, adhesion properties, corrosion resistance, conductivity, and conductor characteristics.
If a solid material to be treated is a porous film, e.g., a fluoroplastic porous film, pores of the fluoroplastic porous film are impregnated with a compound having an atom with a bonding energy to a fluorine atom of 128 kcal/mol or more and a hydrophilic group or a lipophilic group. In this state radiation with a photon energy of 128 kcal or more can be irradiated to modify the fluoroplastic porous film.
By irradiating radiation with a photon energy of 128 kcal or more in this fashion, the Cxe2x80x94F bond (128 kcal/mol) of the fluoroplastic is broken. In this case, by allowing an atom with energy higher than the Cxe2x80x94F bonding energy to exist, the fluorine atom thus broken is bonded to the atom and trapped. Since a fluorine atom has a large electronegativity of 4.0, recombination of C and F can be prevented by making an atom with an electronegativity smaller than that of a carbon atom (electronegativity: 2.5) exist. Also, the bond between this atom and a fluorine atom is difficult to break again, since the bonding energy of this bond is higher than that of the Cxe2x80x94F bond (128 kcal/mol). Therefore, some fluorine atoms of the fluoroplastic can be substituted with a hydrophilic functional group.
The radiation in this case can be selected from the group consisting of an excimer laser, an Ar+ laser, a Kr+ laser, an N2 laser, a harmonics ultraviolet laser obtained by a nonlinear material, a D2 lamp, a high-pressure mercury lamp, a low-pressure mercury lamp, an Xe lamp, an Hgxe2x80x94Xe lamp, a halogen lamp, an excimer lamp, and an ultraviolet lamp obtained by an arc, corona, or silent discharge in an atmosphere of air, nitrogen, or some other gas.
The compound described above can be selected from the group consisting of a boron compound, an aluminum compound, a hydrogen compound, a barium compound, a gallium compound, a lithium compound, and a titanium compound.
The porous body for use in the present invention is not particularly limited. In the case of a fluoroplastic porous body, examples other than PTFE are a tetrafluoroethylene-hexafluoropropylene copolymer, an ethylene-tetrafluoroethylene copolymer, a tetrafluoroethylene-perfluoroalkylvinylether copolymer, a vinyl fluoride resin, a vinylidene fluoride resin, and an ethylene chloride trifluoride resin.
This porous body can take any given shape, such as a sheet or a tube, and can be either a calcined or non-calcined product. The porosity and nominal pore size of the porous body can be freely set in accordance with the intended use. However, it is usually preferable that the porosity be 20 to 80% and the nominal pore size be about 0.01 to 10 xcexcm.
A compound to be used in this case as a modification medium can be any of those enumerated above. These compounds can be used in the form of an aqueous solution and can be added with an alkali salt, such as sodium hydroxide or potassium hydroxide, in order to increase the solubility of the solute.
As a method of impregnating a porous body with the compound, any given simple method such as impregnation or coating can be employed. A porous body can also be subjected to ultrasonic cleaning in advance by dipping in an organic solvent.
As an example, various methods can be used in impregnating pores of a fluoroplastic porous body with the aqueous compound solution. It is, however, preferable to employ the following methods when the hydrophobicity of this porous body is taken into account.
(1) A method of performing impregnation through:
(a) the first step of dipping a fluoroplastic porous body into an organic solvent (e.g., methanol, ethanol, acetone, ether, or isopropylalcohol) having a high compatibility with water and a surface tension of 30 dyne/cm or less, thereby impregnating the porous body with the solvent;
(b) the second step of dipping the resultant porous body in water to replace the solvent with water (impregnate pores with water); and
(c) the third step of dipping the porous body in an aqueous compound solution to replace water with the aqueous solution (impregnate pores with the aqueous solution).
(2) A method in which a compound is mixed in a low-surface-tension organic solvent as described above to prepare a solvent with a surface tension of 30 dyne/cm or less, and the resultant solvent is coated or sprayed on a fluoroplastic porous body, or the fluoroplastic porous body is dipped in the solvent, thereby impregnating pores of the fluoroplastic porous body with the aqueous compound solution.
With this method, it is possible to easily obtain a hydrophilic fluoroplastic porous film having a high hydrophilicity and improved in durability, chemical resistance, solvent resistance, and heat resistance, without performing any vacuum operation such as a discharge process.
As an apparatus using capillarity mentioned above, the present invention provides a solid surface modification apparatus comprising a table for placing a solid material to be treated, a plate-like transparent window capable of being placed on the upper surface of the solid material placed on the table, illuminating means for irradiating ultraviolet radiation, visible radiation, or infrared radiation substantially perpendicularly on the upper surface of the solid material placed on the table, wherein a thin layer of a liquid compound or of a compound solution is interposed between the solid material and the plate-like transparent window by using capillarity, and in this state light is irradiated from the illuminating means onto the upper surface of the solid material to modify the solid surface.
This illuminating means can be so arranged as to selectively irradiate the upper surface of the solid material to be treated with ultraviolet radiation, visible radiation, or infrared radiation.
As an apparatus using a capillary phenomenon, the present invention also provides a solid surface modification apparatus comprising a rotatable rubber roller, a cylindrical transparent round rod or transparent pipe capable of rotating and placed parallel to the rubber roller, means for passing a sheet-like solid material to be treated between the rubber roller and the cylindrical transparent round rod or transparent pipe, illuminating means for linearly irradiating ultraviolet radiation, visible radiation, or infrared radiation to a position at which the rubber roller and the cylindrical transparent round rod or transparent pipe oppose each other, and means for urging the rubber roller and the cylindrical transparent round rod or transparent pipe against each other via the sheet-like solid material, wherein a thin layer of a liquid compound or of a compound solution is interposed between the sheet-like solid material and the cylindrical transparent round rod or transparent pipe by using capillarity, and in this state light is irradiated from the illuminating means onto the upper surface of the solid material to continuously modify the solid surface.
This illuminating means can be arranged outside the cylindrical transparent round rod or transparent pipe. Alternatively, the illuminating means can consist of a reflecting mirror arranged inside the transparent pipe and means for emitting a linear beam from an end portion of the pipe, or can be an elongated lamp inserted inside the transparent pipe. That is, the illuminating means can be properly chosen from these structures.
As an apparatus using capillarity, the present invention further provides a method of modifying the surface of a lens, wherein a lens to be subjected to a surface treatment is sandwiched between a concave lens and a convex lens, thin layers of a compound solution are interposed between the lens to be treated (e.g., a contact lens) and the concave lens and between the lens to be treated and the convex lens by capillarity, and in this state light is irradiated on both the surfaces of the lens to be treated to modify the surfaces.
In addition, the present invention provides a method in which a transparent liquid plastic (e.g., silicon rubber, fluoroplastic, or PMMA) is flowed on the surface of a solid material to be treated, which assumes a complicated shape, to form a mold, and the mold is hardened and released. Thereafter, a thin layer of a compound solution is interposed between this mold and the surface of the solid material to be treated (e.g., a denture) by using capillarity, and light is irradiated from the mold side onto the surface of the solid material, thereby modifying the surface.
Furthermore, the present invention provides an apparatus in which a window is formed into a donut-like shape, and a thin liquid film layer is interposed between the surface of a solid material to be treated (e.g., a sheath of an electric wire or a jacket of a tube), which corresponds to the inner circumferential surface of the donut-like window, and the inner circumferential surface of the window by using a capillary phenomenon. In this apparatus, the surface of the solid material whose outer circumference is a circle can be continuously modified by irradiating light on the surface from the outer circumferential surface of the window. By arranging a plurality of these apparatuses, more effective surface modification can be performed.
Moreover, it is found that when water, an oil, or an adhesive is interposed between fluoroplastic sheets or between a fluoroplastic sheet and a material to be adhered, and ArF excimer laser light is irradiated through the fluoroplastic sheet while closely adhering these materials by pressure, these fluoroplastic sheets or the fluoroplastic sheet and the material to be adhered are strongly chemically adhered to each other according to the present invention. The reason for this is assumed that hydrogen atoms optically dissociated from water (H2O) or oil liberate fluorine atoms from the surface of the fluoroplastic sheet, oxygen atoms dissociated from water or oil are substituted to the positions from which the fluorine atoms are released, and consequently nonbonded hands on the surface of the fluoroplastic sheet have the same oxygen atom in common to give a strong adhesive force.
This similarly applies to an adhesive; that is, it is assumed that hydrogen atoms optically dissociated from an adhesive liberate fluorine atoms from the surface of a fluoroplastic sheet which is simultaneously excited, and nonbonded hands of the adhesive which has lost hydrogen atoms are bonded to the positions from which the fluorine atoms are released, resulting in a strong adhesion force.
According to the present invention, it is also found that an antithrombotic material required for an artificial blood vessel or organ can be readily formed by the use of a fluoroplastic material.
When coherent light radiated from a single light source such as a laser is split into two optical paths and again incident at respective certain angles, interference takes place at the intersection of these light components. Generally, a material coated with a sensitizing agent is placed on this interference portion. In the present invention, however, a transparent window is placed on the surface of a solid material to be treated via a compound liquid film, and ultraviolet laser beams incident through the transparent window from two or more directions are caused to interfere with each other on the interface between the surface of the solid material and the liquid layer. Consequently, only a portion of the surface of the solid material corresponding to the portion of interference is photochemically modified.
Especially when two light beams are incident from two directions while their respective Brewster angles are maintained, only p-polarized light is incident inside the window. This permits high-efficiency modification in the form of a diffraction grating.
Also, a partial side surface of a window is formed into a plane mirror, and ultraviolet radiation is irradiated obliquely from the side away from the side of the plane mirror such that light directly propagating through the window and light reflected by the internal plane mirror interfere with each other. The result is modification in a diffraction-grating form on the surface of the solid material via the window and a thin layer of a compound liquid film. Especially when the angle of incidence of ultraviolet laser light to be obliquely incident is maintained at a Brewster angle, only p-polarized light brings about interference, resulting in a high interference efficiency. When the surface of a material is modified in the form of a grating, e.g., when a hydrophilic group is substituted in a grating form by using a fluoroplastic material as a solid material to be treated, a hydrophilic or hydrophobic micro domain structure is formed. This allows easy formation of an antithrombotic material necessary for an artificial blood vessel or organ by the use of a fluoroplastic material.
As discussed earlier, the angle of contact between a substance to be modified and a liquid is large. For this reason, the contact area with the surface of a sample becomes small, and bubbles generated by photo-decomposition further decrease the contact area. As in the present invention, however, by keeping the sample and the glass surface in tight contact with each other and interposing a compound solution between them by using capillarity, an even thin liquid film can be formed on the entire surface of the sample. When ultraviolet radiation is incident from the side of the glass surface, the liquid is locally, optically decomposed, and the surface of the sample is also excited with a fraction of light transmitted through the liquid, bringing about a chemical reaction. Additionally, since the liquid film is thin, all parts of the decomposition product are consumed in the surface treatment, so no excess reaction product which causes generation of bubbles forms. Consequently, no bubbles are generated, making a highly efficient surface treatment possible.